Evaluation of mycelial inocula of edible Lactarius species for the production of Pinus pinaster and P. sylvestris mycorrhizal seedlings under greenhouse conditions

Different methods to inoculate seedlings of Pinus pinaster and P. sylvestris with edible Lactarius species under standard greenhouse conditions were evaluated. Fungal inoculations were performed both under pure culture synthesis in vitro, followed by transplantation of acclimatized seedlings, and directly in the greenhouse using different techniques for inocula production (mycelial slurries, vegetative inoculum grown in peat-vermiculite and alginate-entrapped mycelium). In vitro inoculations with L. deliciosus produced thoroughly colonized seedlings. However, a sharp decrease in mycorrhizal colonization was detected on transplanted seedlings after 4 month's growth in the greenhouse. On the other hand, all the inocula applied directly in the greenhouse, except the alginate-entrapped mycelium, produced a variable number of mycorrhizal seedlings and colonization rates after the first growing season, depending on the plant-fungal combination and the inoculation method. Inoculations with vegetative inocula of the strain 178 of L. deliciosus were the most effective in producing mycorrhizal seedlings. All the seedlings inoculated with this strain were colonized although the colonization rates were relatively low. The commercial feasibility of the different inoculation methods for the production of seedlings colonized with edible Lactarius species is discussed.     

Interactions between<Emphasis Type="Italic"> Trichoderma pseudokoningii</Emphasis> strains and the arbuscular mycorrhizal fungi<Emphasis Type="Italic"> Glomus mosseae</Emphasis> and<Emphasis Type="Italic"> Gigaspora rosea</Emphasis>

The interaction between Trichoderma pseudokoningii (Rifai) 511, 2212, 741A, 741B and 453 and the arbuscular mycorrhizal fungi Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe BEG12 and Gigaspora rosea Nicolson & Schenck BEG9 were studied in vitro and in greenhouse experiments. All T. pseudokoningii strains inhibited the germination of G. mosseae and Gi. rosea except the strain 453, which did not affect the germination of Gi. rosea. Soluble exudates and volatile substances produced by all T. pseudokoningii strains inhibited the spore germination of G. mosseae. The germination of Gi. rosea spores was inhibited by the soluble exudates produced by T. pseudokoningii 2212 and 511, whereas T. pseudokoningii 714A and 714B inhibited the germination of Gi. rosea spores by the production of volatile substances. The strains of T. pseudokoningii did not affect dry matter and percentage of root length colonization of soybean inoculated with G. mosseae, except T. pseudokoningii 2212, which inhibited both parameters. However, all T. pseudokoningii strains decreased the shoot dry matter and the percentage of AM root length colonization of soybean inoculated with Gi. rosea. The saprotrophic fungi tested seem to affect AM colonization of root by effects on the presymbiotic phase of the AM fungi. No influence of AM fungi on the number of CFUs of T. pseudokoningii was found. The effect of saprotrophic fungi on AM fungal development and function varied with the strain of the saprotrophic species tested.     

Improvement by soil yeasts of arbuscular mycorrhizal symbiosis of soybean (<Emphasis Type="Italic">Glycine max</Emphasis>) colonized by<Emphasis Type="Italic"> Glomus mosseae</Emphasis>

The effects of the soil yeasts Rhodotorula mucilaginosa, Cryptococcus laurentii and Saccharomyces kunashirensis on the arbuscular mycorrhizal (AM) fungus Glomus mosseae (BEG 12) was studied in vitro and in greenhouse trials. The presence of yeasts or their soluble and volatile exudates stimulated the percentage spore germination and hyphal growth of G. mosseae. Percentage root length colonized by G. mosseae and plant dry matter of soybean (Glycine max L. Merill) were increased only when the soil yeasts were inoculated prior to the AM fungus. Higher beneficial effects on AM colonization and plant dry matter were found when the soil yeasts were inoculated as an aqueous solution rather than as a thin agar slice. Although soluble and volatile exudates of yeasts benefited the AM symbiosis, their modes of action were different.This revised version was published online in May 2004 with corrections to the section of the article.     

Synthesis and establishment of <Emphasis Type="Italic">Tuber melanosporum</Emphasis> Vitt. ectomycorrhizae on two <Emphasis Type="Italic">Nothofagus</Emphasis> species in Chile

Axenically germinated seedlings of two species of Southern beech (Nothofagus obliqua, N. glauca) from Chile were inoculated with spores of the Périgord black truffle (Tuber melanosporum). Ectomycorrhizal development was monitored for 6 months in the greenhouse and compared to the performance of the natural host species Quercus ilex and Quercus robur. Seedling survival and mycorrhization showed major differences in both Nothofagus species: T. melanosporum readily formed ectomycorrhizae with seedlings of N. obliqua, although at a lower rate than with Q. ilex but at a proportion very similar to Q. robur; survival and colonization rates were high, and seedling growth was not visibly affected by the high soil pH required by T. melanosporum. In contrast, more than 50% of N. glauca seedlings died after inoculation, and mycorrhiza formation was very sparse. In both species, no colonization by adventive ectomycorrhizal fungi could be observed, whereas both species of Quercus showed minor colonization by another fungus, probably Inocybe or Hebeloma. Our results show that it is possible to infect N. obliqua with the Périgord black truffle under greenhouse conditions, which opens up the possibility of cultivating this truffle as a secondary crop during reforestation with N. obliqua in Chile.     

Behaviour of the hyphae of<Emphasis Type="Italic"> Laccaria laccata</Emphasis> in the presence of<Emphasis Type="Italic"> Trichoderma harzianum</Emphasis> in vitro

The growth rate and the behaviour of Laccaria laccata and Trichoderma harzianum hyphae in co-culture and in the rhizosphere of 3-month-old Pinus sylvestris seedlings grown in vitro were investigated. In the interaction zone, hyphae of L. laccata became more pigmented and formed short branches growing towards the hyphae of the saprobic fungus, coiled around them and penetrated sporadically. Vacuolated hyphae of T. harzianum showed protoplasm granulation and breaks in walls followed by release of protoplasts. In the rhizosphere, the mantle hyphae of L. laccata showed a tendency to surround conidia of T. harzianum. No obvious penetration of the conidial walls by the hyphae of the mycorrhizal fungus was observed by scanning electron microscopy. Instead, in rare cases, the hyphae of L. laccata showed marked wrinkles, and a partial degradation of a mucilaginous material covering the mantle appeared to occur.     

Interaction of <Emphasis Type="Italic">Azospirillum brasilense</Emphasis> and <Emphasis Type="Italic">Glomus intrarradix</Emphasis> in Sugar Cane Roots

Fifteen-day-old variety NA 56-79 sugar cane seedlings were inoculated with Azospirillum brasilense and Glomus intrarradix. This article aims at examining changes in sugar cane root seedlings inoculated with Glomus intrarradix and Azospirillum brasilense, the increase in microbial biomass and the acetylene reduction process as well. The internal root colonization was studied 20 days after inoculation using scanning and a transmission electron microscope. Both microorganisms entered the sugar cane root through the emergent lateral roots. The microorganisms were capable of coexisting both intra and intercellularly, producing changes in the cell wall, thus allowing colonization and interaction between the organisms. These changes increased the number of microorganisms inside the root as well as acetylene nitrogen reduction. Sugar cane plant biomass increased with joint-inoculation. The number of endophytic microorganisms and nitrogen fixing activity increased when they were colonized by Azospirillum and Glomus together.     

Establishment of mycorrhizal symbiosis in<Emphasis Type="Italic">Gentiana verna</Emphasis>

The last lowland locality ofGentiana verna in the Czech Republic is a calcareous grassland near Rovná at Strakonice in South Bohemia. This locality was the subject of a recovery programme that included support of the remaining population by micropropagation. The plants were inoculated with arbuscular mycorrhizal fungi (AMF) after their transfer toex vitro and the effect of AMF on their establishment and survival was studied. Although the conventional method of inoculation ofG. verna using spores or colonized root segments as an inoculum source resulted in no or negligible root colonization, the transplantation of gentians to the locality Rovná was successful and the plants became colonized with AMF very rapidly in the field. Successful mycorrhization of gentians under experimental conditions occurred only via the extraradical mycelial network established by neighbouring mycorrhizal plant species (nurse plant effect). Different nurse plant species formed different morphological types of mycorrhiza when inoculated with the same fungal isolate. Gentians always had theParis type of root colonization with intracellular hyphal loops and swellings. Intercellular hyphae, arbuscules and vesicles were not observed. No evidence for a positive growth response was found inG. verna.     

Phenotypic alterations in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis> plants caused by<Emphasis Type="Italic"> Rhodococcus fascians</Emphasis> infection

Arabidopsis thaliana (L.) Heynh. plants were challenged with Rhodococcus fascians at several developmental stages and using different inoculation procedures. A variety of morphological alterations was scored on the infected plants; some of them resembled phenotypes of A. thaliana mutants in their shoot apical meristem (SAM) organization. Infection with R. fascians did not affect SAM organization in wild type nor in SAM mutants. Anatomical studies on the new organs formed after infection with R. fascians demonstrated extensive bacterial colonization. Colonization and concomitant production of specific signals are the likely cause of malformations.     

Influence of colonisation by an arbuscular mycorrhizal fungus on the growth of seedlings of<Emphasis Type="Italic"> Banksia ericifolia</Emphasis> (Proteaceae)

Tap and primary lateral roots of seedlings of the putatively non-mycorrhizal Banksia ericifolia became marginally colonised when grown in an established mycelium of an arbuscular mycorrhizal (AM) fungus in the laboratory. A similar degree of colonisation was found in seedlings from an open woodland. All colonies lacked arbuscules. Two factors influencing colonisation and associated growth of host plants were examined experimentally: concentration of P in the soil and organic energy associated with the fungus. While some inoculated seedlings were slightly smaller when colonised by AM fungi, the results were inconsistent and never statistically significant. Seedlings take up insignificant quantities of soil P during early growth, even in the presence of abundant added P. Though colonisation was minor in all cases, an existing mycelium, whether or not connected to a companion plant, slightly increased the amount of root of B. ericifolia colonised by an AM fungus. All seedlings grew slowly. Shoots were significantly larger than roots, until the initiation of proteoid roots which commenced at about 40 days after germination, with both relatively high and low P supply.     

Effect of<Emphasis Type="Italic">Glomus intraradices</Emphasis> isolated from Pb-contaminated soil on Pb uptake by<Emphasis Type="Italic">Agrostis capillaris</Emphasis> is changed by its cultivation in a metal-free substrate

Development and heavy metal tolerance of two cultivation lineages of the indigenous isolate of arbuscular mycorrhizal fungus (AMF)Glomus intraradices PH5 were compared in a pot experiment in soil from lead (Pb) smelter waste deposits. One lineage was sub-cultured in original Pb-contaminated soil; the second one was maintained for 13 months in an inert substrate (river sand) without Pb stress. The contribution of these cultivation lineages to the Pb uptake and accumulation by the host plantAgrostis capillaris was investigated. The experiment was conducted in a compartmented system where the lateral compartments withAgrostis seedlings were separated from the central pot containing 4-week olderAgrostis plants by a nylon mesh for allowing out-growing of extraradical mycelium (ERM) from the pot. No differences in mycorrhizal colonization, ERM length and viability were observed between the two lineages ofG. intraradices PH5 in the soil of the isolate origin. However, the ability to support plant growth and Pb uptake differed between the lineages and also between the plants in the central pots and the lateral compartments. The growth of the plants in the central pots was positively affected by AMF inoculation. The plants inoculated with the lineage maintained in original soil showed larger shoot biomass and higher shoot P content as compared to the other inoculation treatments. The shoot Pb concentration of these plants was lower when compared to the plants inoculated with the lineage sub-cultured in the inert substrate. However the concentration did not differ from non-mycorrhizal control or from the reference isolateG. intraradices BEG75 from non-contaminated soil. Also shoot Pb contents were similar for all inoculation treatments. The development ofG. intraradices BEG75 in the contaminated soil was very poor; this isolate was not able to initiate colonization of seedlings in lateral compartments. In lateral compartments, growth of seedlings in contaminated soil was inhibited by theG. intraradices PH5 lineage maintained in the inert substrate. Pb translocation from the seedling roots to shoots was increased for plants inoculated with either lineage as compared to the non-mycorrhizal control; however, the increase for the lineage cultivated in the inert substrate was significantly higher in comparison with that maintained in the original soil. After 13 months of cultivation in a metal free substrate, theG. intraradices isolate from Pb contaminated soil did not lose its tolerance to Pb as regards colonization of plant roots and growth of ERM in the soil of its origin. However, its ability to support plant growth and to prevent Pb translocation from the roots to the shoots was decreased.     

Mycorrhizal inoculant alleviates salt stress in<Emphasis Type="Italic"> Sesbania aegyptiaca</Emphasis> and<Emphasis Type="Italic"> Sesbania grandiflora</Emphasis> under field conditions: evidence for reduced sodium and improved magnesium uptake

A field experiment was conducted to examine the effect of the arbuscular mycorrhizal fungus Glomus macrocarpum and salinity on growth of Sesbania aegyptiaca and S. grandiflora. In the salt-stressed soil, mycorrhizal root colonisation and sporulation was significantly higher in AM-inoculated than in uninoculated plants. Mycorrhizal seedlings had significantly higher root and shoot dry biomass production than non-mycorrhizal seedlings grown in saline soil. The content of chlorophyll was greater in the leaves of mycorrhiza-inoculated as compared to uninoculated seedlings. The number of nodules was significantly higher in mycorrhizal than non-mycorrhizal plants. Mycorrhizal seedling tissue had significantly increased concentrations of P, N and Mg but lower Na concentration than non-mycorrhizal seedlings. Under salinity stress conditions both Sesbania sp. showed a high degree of dependence on mycorrhizae, increasing with the age of the plants. The reduction in Na uptake together with a concomitant increase in P, N and Mg absorption and high chlorophyll content in mycorrhizal plants may be important salt-alleviating mechanisms for plants growing in saline soil.     

Genes expressed in zoospores of<Emphasis Type="Italic"> Phytophthora nicotianae</Emphasis>

The genus Phytophthora includes many highly destructive plant pathogens. In many Phytophthora species, pathogen dispersal and initiation of plant infection are achieved by motile, biflagellate zoospores that are chemotactically attracted to suitable infection sites. In order to study gene expression in zoospores, we have constructed a cDNA library using mRNA from zoospores of Phytophthora nicotianae. The library was arrayed and screened using probes derived from mycelium or zoospore mRNA. More than 400 clones representing genes preferentially expressed in zoospores were identified and sequenced from the 5 end of the insert. The expressed sequence tags (ESTs) generated were found to represent 240 genes. The ESTs were compared to sequences in GenBank and in the Phytophthora Genome Consortium database, and classified according to putative function based on homology to known proteins. To further characterize the identified genes, a colony array was created on replicate nylon filters and screened with probes derived from four Phytophthora developmental stages including zoospores, germinating cysts, vegetative mycelium and sporulating hyphae, and from inoculated and uninoculated tobacco seedlings. Data from sequence analysis and colony array screening were compiled into a local database, and searched to identify genes that are preferentially expressed in zoospores for future functional analysis.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by C. A. M. J. J. van den Hondel     

The mycorrhizal fungus<Emphasis Type="Italic"> Tricholoma matsutake</Emphasis> stimulates<Emphasis Type="Italic"> Pinus densiflora</Emphasis> seedling growth in vitro

While it has been suggested that Matsutake mycorrhizae might not be functional and that Matsutake may behave as a saprobic fungus in soil or even have some pathogenic activity on seedlings, we investigated the consequences of Matsutake inoculation on Pinus densiflora growth. Seventy-five days after inoculation, hyphae were anchored on short roots and well-developed Hartig net palmettis were observed. Compared to both control treatments—seedlings treated with distilled water and seedlings treated with autoclaved mycelium—inoculation significantly stimulated seedling total dry weight by 70.9% and 98.0%, respectively. These findings attest that some type of symbiotic relationship must be functional and favour host growth, ruling out claims of pathogenicity under the sterile conditions used here.     

Inoculation of<Emphasis Type="Italic">Rhododendron</Emphasis> cv. Belle-Heller with two strains of<Emphasis Type="Italic">Phialocephala fortinii</Emphasis> in two different substrates

The growth response of an ornamentalRhododendron hybrid to the inoculation withPhialocephala fortinii was studied in two pot experiments in order to decide about the effectiveness of the inoculation of young rhododendron microplants. Two different substrates were used in both experiments, either sterilized or non-sterilized: a horticultural substrate and a soil collected from a field site with dominant ericoid vegetation. Two fungal isolates were used for an inoculation:P. fortinii strain P (UAMH 8433) andP. fortinii strain F, a dark septate endophyte (DSE) previously isolated from naturally-infected roots ofVaccinium myrtillus. BothPhialocephala strains successfully colonized the roots of the host plants forming typical DSE (=pseudomycorrhizal) colonization pattern including the formation of intracellular microsclerotia. However, pseudomycorrhizal colonization did not affect the growth parameters of the host rhododendrons. The results from both experiments indicate a neutral effect of the inoculation with DSE fungi on the growth ofRhododendron cv. Belle-Heller.     

Differential responses of three fungal species to environmental factors and their role in the mycorrhization of<Emphasis Type="Italic"> Pinus radiata</Emphasis> D. Don

Three ectomycorrhizal (ECM) isolates of Rhizopogon luteolus, R. roseolus and Scleroderma citrinum were found to differ markedly in their in vitro tolerance to adverse conditions limiting fungal growth, i.e. water availability, pH and heavy metal pollution. S. citrinum was the most sensitive, R. luteolus intermediate and R. roseolus the most tolerant species. Pinus radiata D. Don seedlings were inoculated in the laboratory and in a containerised seedling nursery with spore suspensions of the three ECM species. Colonisation percentage was considerably lower under nursery conditions, probably due to competition by native fungi. The effects of nursery ECM inoculation on seedling growth depended on the fungal species. Only R. roseolus-colonised plants showed a significantly higher shoot growth than non-mycorrhizal plants. All three fungi induced significantly higher root dry weights relative to control plants. Despite the low mycorrhizal colonisation, mycorrhization with all three species improved the physiological status of nursery-grown seedlings, e.g. enhanced root enzyme activity, shoot nutrient and pigment content, net photosynthesis rate and water use efficiency. Of the three fungal species, R. roseolus was the most effective; this species was also the most adaptable and showed the greatest range of tolerance to adverse environmental conditions in pure culture. It is, therefore, proposed as a promising fungal species for ECM inoculation of P. radiata in the nursery.     

<Emphasis Type="Italic">AOM3</Emphasis> and<Emphasis Type="Italic"> AOM4</Emphasis>: two MADS box genes expressed in reproductive structures of<Emphasis Type="Italic"> Asparagus officinalis</Emphasis>

The MADS box genes participate in different steps of vegetative and reproductive plant development, including the most important phases of the reproductive process. Here we describe the isolation and characterisation of two Asparagus officinalis MADS box genes, AOM3 and AOM4. The deduced AOM3 protein shows the highest degree of similarity with ZAG3 and ZAG5 of maize, OsMADS6 of rice and AGL6 of Arabidopsis thaliana. The deduced AOM4 protein shows the highest degree of similarity with AOM1 of asparagus, the SEP proteins of Arabidopsis and the rice proteins OsMADS8, OsMADS45 and OsMADS7. The high level of identity between AOM1 and AOM4 made impossible the preparation of probes specific for one single gene, so the hybridisation signal previously described for AOM1 is probably due to the expression of both genes. The expression profile of AOM3 and AOM1/AOM4 during flower development is identical, and similar to that of the SEP genes. Asparagus genes, however, are expressed not only in flower organs, but also in the different meristem present on the apical region of the shoot during the flowering season: the apical meristem and the three lateral meristems emerging from the leaf axillary region that will give rise to flowers and lateral inflorescences during flowering season, and to phylloclades and branches during the subsequent vegetative phase. The expression of AOM3 and AOM1/AOM4 in these meristems appears to be correlated with the reproductive function of the apex as the hybridisation signal disappears when the apex switches to vegetative function.     

Mycorrhizal synthesis between <Emphasis Type="Italic">Lactarius deliciosus</Emphasis> and <Emphasis Type="Italic">Arbutus unedo</Emphasis> L.

Arbutoid mycorrhizae were synthesized in vitro between Arbutus unedo L. and two isolates of Lactarius deliciosus. The fungal isolates were obtained from sporocarps collected under Pinus sylvestris and in a mixed forest stand of Quercus suber and Pinus pinea. Synthesis tubes filled with a mixture of sterilized peat, vermiculite, and perlite imbibed with nutrient solution were used. Two inoculation methods using solid and liquid media were tested. Shoots from an adult selected clone of A. unedo were used after in vitro rooting by auxin dipping. After 3 months of shoots transfer to the substrate, the root systems were examined for arbutoid mycorrhizae formation and later on ex vitro conditions, 9 months after acclimatization. The inoculum treatment with liquid medium improved the mycorrhizal development for both isolates, in vitro. Sterilized substrate for plant acclimatization increased the mycorrhizal development. The arbutoid mycorrhizae were observed in vitro as well as 9 months after acclimatization. Standard arbutoid mycorrhiza features were observed: pale yellow mantle, typical cruciform appearance, Hartig net (HN), and intracellular hyphal complexes, both confined to the epidermis. L. deliciosus mycorrhizae synthetized in vitro persisted 9 months after plant acclimatization. Morphological observations were confirmed by molecular techniques.     

A rapid<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> transient assay system

Stable transformation ofArabidopsis thaliana is a lengthy process that involves up to 3 mo of plant growth and seed selection. We have developed a rapid, 3-wk transient assay system to test the functionality ofcis-regulatory regions controlling expression of a reporter gene in plants before undertaking stable transformation. Two-week-oldArabidopsis seedlings were vacuum-infiltrated withAgrobacterium tumefaciens cultures carrying various upstream regulatory regions controllinguidA (β-glucuronidase [GUS]) expression. Seedlings were fixed and stained for GUS activity 3–5 d following infiltration. Regulatory regions tested in this system include the cauliflower mosaic virus (CaMV)35S promoter, the upstream regulatory region of ribosomal protein geneL23A-1, and a temperature-inducible regulatory region (HSP101B) also fromArabidopsis. The percentage of seedlings positive for GUS activity varied depending on the construct used, with the CaMV35S promoter producing the highest number of GUS-positive seedlings. Temperature induction treatments elicited increased GUS expression in seedlings transformed with theHSP101B regulatory region. Regardless of construct, GUS expression levels were higher in seedlings collected 5 d followingAgrobacterium infiltration than those collected 3–4 d postinfiltration.     

<Emphasis Type="Italic">Penicillium frequentans</Emphasis> isolated from<Emphasis Type="Italic"> Picea glehnii</Emphasis> seedling roots as a possible biological control agent against damping-off

Picea glehnii seedlings are affected by damping-off fungi in nurseries. The aims of this study were (1) to isolate fungi grown in the seedling rhizosphere in forest soil of P. glehnii, (2) to select fungi that produce antifungal compounds against Pythium vexans, and (3) to examine whether or not selected fungi can protect seedlings from P. vexans. Penicillium frequentans from Picea glehnii seedling roots produced antibiotic penicillic acid. Penicillic acid did not cause significant phytotoxicity to the seedlings. Penicillium frequentans increased the average percentage of surviving seedlings when inoculated together with Pythium vexans, but the increase was not significant. Vigorous mycelial growth of P. frequentans around seedling roots seems to be one of the mechanisms for protection, but the amount of penicillic acid was too low to show antifungal activity in the seedling rhizosphere.     

<Emphasis Type="Italic">Piriformospora indica</Emphasis> and <Emphasis Type="Italic">Sebacina vermifera</Emphasis> increase growth performance at the expense of herbivore resistance in <Emphasis Type="Italic">Nicotiana attenuata</Emphasis>

A Sebacinales species was recovered from a clone library made from a pooled rhizosphere sample of Nicotiana attenuata plants from 14 native populations. Axenic cultures of the related species, Piriformospora indica and Sebacina vermifera, were used to examine their effects on plant performance. Inoculation of N. attenuata seeds with either fungus species stimulated seed germination and increased growth and stalk elongation. S. vermifera inoculated plants flowered earlier, produced more flowers and matured more seed capsules than did non-inoculated plants. Jasmonate treatment during rosette-stage growth, which slows growth and elicits herbivore resistance traits, erased differences in vegetative, but not reproductive performance resulting from S. vermifera inoculation. Total nitrogen and phosphorous contents did not differ between inoculated and control plants, suggesting that the performance benefits of fungal inoculation did not result from improvements in nutritional status. Since the expression of trypsin proteinase inhibitors (TPI), defensive proteins which confer resistance to attack from Manduca sexta larvae, incur significant growth and fitness costs for the plant, we examined the effect of S. vermifera inoculation on herbivore resistance and TPI activity. After 10 days of feeding on S. vermifera-inoculated plants, larval mass was 46% higher and TPI activity was 48% lower than that on non-inoculated plants. These results suggest that Sebacina spp. may interfere with defense signaling and allow plants to increase growth rates at the expense of herbivore resistance mediated by TPIs.